The present invention relates to a two-speed fuel injection pump governor especially suited to a compression ignition or Diesel engine.
In a known two-speed governor, the centrifugal force developed by flyweights is balanced against the forces of high and low speed governor springs. When the engine speed exceeds a predetermined maximum value, the flyweights overcome the preload of the high speed governor spring and move a fuel control rod to decrease the amount of fuel injection and reduce the engine speed to the maximum value. When the engine speed drops below a predetermined minimum value the flyweights and thereby the control rod are moved by the low speed governor spring to increase the amount of fuel injection and increase the engine speed to the minimum value. A manual speed control member such as an accelerator pedal moves the fuel control rod to control the engine speed between the minimum and maximum values in which case the engine speed depends on the position of the speed control member and the engine load.
The flyweights and low speed governor spring are designed to supply sufficient fuel into the engine to prevent stalling under no-load conditions. However, when the engine speed drops below the minimum value with the engine operating under load, a proportionately smaller amount of fuel injection increase is required to raise the engine speed to the minimum value. As a result, excessive fuel is injected during minimum speed regulation with the engine operating under load which results in incomplete combustion and the emission of pollutants into the atmosphere.